JP3212639B2 - Non-aqueous solvent secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous solvent secondary battery, and more particularly to a non-aqueous solvent secondary battery having an improved active material for a positive electrode.

[0002]

2. Description of the Related Art In recent years, non-aqueous solvent batteries using a light metal such as lithium, sodium, or aluminum as a negative electrode active material have attracted attention as high energy density batteries, and manganese dioxide (MnO ₂ ) and fluorine have been used as positive electrode active materials. Carbonized [(C
F _n )], primary batteries using thionyl chloride (SOCl ₂ ) and the like are already widely used as backup batteries for power supplies for calculators, watches and memories. Further, in recent years, with the miniaturization and weight reduction of various electronic devices such as VTRs and communication devices, demands for secondary batteries having a high energy density as a power source for these devices have increased, and non-aqueous solvents using light metals as negative electrode active materials have been required. Research on secondary batteries is being actively conducted.

A non-aqueous solvent secondary battery uses a light metal such as lithium, sodium, or aluminum as a negative electrode, and uses propylene carbonate (PC), 1,2-dimethoxyethane (DME), γ-butyrolactone (γ-BL) as an electrolyte. ), LiClO in a non-aqueous solvent such as tetrahydrofuran (THF)
₄ , LiBF ₄ , LiAsF ₆ , LiPF _6, etc., which are formed by dissolving lithium salts. As the positive electrode active material, TiS ₂ , MoS ₂ , V ₂ O ₅ , V ₆ O _13, etc. are mainly studied. . More recently, LiMn ₂ O 4, LiC
oO ₂ , LiNiO _2, etc. are delithiated and 4V
Therefore, these positive electrode active materials are expected to have a higher energy density. However, when the voltage is increased, there is a problem that the electrolyte is oxidatively decomposed and the charge / discharge cycle life characteristic is deteriorated.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a non-aqueous solvent secondary battery having excellent charge / discharge cycle characteristics and large current charge / discharge characteristics. It is assumed that.

[0005]

A non-aqueous solvent secondary battery according to the present invention comprises a negative electrode made of lithium, a lithium alloy or a compound containing lithium, LiCoO ₂ and LiNi.
A non-aqueous solvent secondary battery including a positive electrode containing at least one selected from O ₂ as a positive electrode active material and an electrolyte solution in which an electrolyte is dissolved in a non-aqueous solvent, wherein phosphorus is added as the positive electrode active material Is used.

The lithium alloy constituting the negative electrode is, for example, LiAl, LiPb, LiSn, LiBi or the like, and the lithium-containing compound is, for example, a conductive polymer such as polyacetal, polyacetylene or polypyrrole doped with lithium ion; And a carbon material made of an organic sintered body doped with a.

The phosphorus (P) added to the positive electrode active material includes phosphorus (P), phosphorus pentoxide (P ₂ O ₅ ), lithium phosphate (Li ₃ PO ₄ ), and lithium dihydrogen phosphate (Li).
H ₂ PO ₄ ), ammonium phosphate [(NH 4) ₃ PO
₄ , 3H ₂ O]. Such phosphorus is used in the LiMn ₂ O ₄ , LiCoO ₂ , LiN
For the active material of iO ₂ , 0.05 to Mn, Co, and Ni
It is desirable to add 0.2 mole ratio.

The LiCoO ₂ added with phosphorus is, for example, (a) cobalt oxide such as CoO, Co ₂ O ₃ , Co ₃ O ₄ or cobalt carbonate (CoCO ₃ ); cobalt nitrate [Co (NO ₃ ) _2. 4H ₂ O] and (b) a lithium salt such as lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium nitrate (LiNO ₃ ) or lithium halide and (c) the phosphorus compound Can be obtained by heating and reacting the mixture.

The above-mentioned phosphorus-added LiNiO ₂ is, for example, (a) nickel oxide such as NiO, Ni ₂ O ₃ , Ni ₃ O ₄ or nickel carbonate (NiCO ₃ ), nickel nitrate [Ni (NO ₃ ) _2. 6H ₂ O] and (b) a lithium salt such as lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium nitrate (LiNO ₃ ) or lithium halide and (c) the phosphorus compound Can be obtained by heating and reacting the mixture.

The positive electrode may be, for example, (1) a pellet formed by molding the positive electrode active material with a conductive material and a binder, and (2) kneading the positive electrode active material with a conductive material and a binder. And (3) a conductive material and a binder suspended in an appropriate solvent in the positive electrode active material, applied to a current collector, and dried to form a film. it can. As the conductive material, for example, acetylene black,
Graphite or the like can be used, and as the binder, for example, polytetrafluoroethylene or the like can be used. The positive electrode active material,
The mixing ratio of the conductive material and the binder is from 80 to
It is desirable that the content is 90% by weight, the conductive material is 5 to 20% by weight, and the binder is 2 to 7% by weight.

The non-aqueous solvent constituting the electrolytic solution includes:
For example, one type or a mixture of two or more types selected from ethylene carbonate, 2-methyltetrahydrofuran, 1,2-dimethoxyethane, diethoxyethane, 1,3-dioxolan, and 1,3-dimethoxypropane can be exemplified. Examples of the electrolyte constituting the electrolyte include lithium borofluoride (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), and lithium perchlorate (LiC ₆ ).
lO ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO
₃ ) and one or more lithium salts selected from lithium aluminum chloride (LiAlCl ₄ ). The amount of the electrolyte dissolved in the non-aqueous solvent is
It is desirably 0.5 to 1.5 mol / l.

[0012]

According to the present invention, LiCoO ₂ containing phosphorus is added.
By using a positive electrode containing at least one positive electrode active material selected from LiNiO ₂ and LiNiO _2, lithium ions can easily move in the positive electrode during charge and discharge, and a charge overvoltage can be reduced. Therefore, a non-aqueous solvent secondary battery having excellent charge / discharge cycle characteristics and high current charge / discharge characteristics can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a cylindrical non-aqueous solvent secondary battery will be described in detail with reference to FIG.

REFERENCE EXAMPLE 1 Reference numeral 1 in the figure denotes a bottomed cylindrical stainless steel container having an insulator 2 disposed at the bottom. In this container 1, an electrode group 3 is housed. The electrode group 3 has a structure in which a band formed by laminating a positive electrode 4, a separator 5 and a negative electrode 6 in this order is spirally wound so that the negative electrode 6 is located outside. The positive electrode 4 was prepared by the following method, the separator 5 was formed of a porous film made of polypropylene, and the negative electrode 6 was formed of a band-shaped lithium foil.

First, manganese trioxide (Mn ₂ O ₃ ), lithium carbonate (Li ₂ CO ₃ ) and phosphorus pentoxide (P
₂ O ₅ ) and a molar ratio of Li: Mn: P = 1.3: 2: 0.1, sufficiently mixed in a mortar, and heat-treated in air at 900 ° C. for 10 hours. X-ray diffraction measurement of the obtained product confirmed that a LiMn ₂ O ₄ phase was present. Subsequently, the phosphorus-added LiMn ₂
80% by weight of O ₄ powder was mixed with 15% by weight of acetylene black and 5% by weight of polytetrafluoroethylene powder, formed into a sheet, and pressed on an expanded metal current collector to produce a band-shaped positive electrode having a width of 40 mm and a length of 200 mm. .

In the container 1, 1.0 mol / l of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solvent of propylene carbonate and 1,2-dimethoxyethane (mixing volume ratio 1: 1). An electrolyte of the composition is contained. On the electrode group 3, an insulating paper 7 having a central opening is placed. Further, an insulating sealing plate 8 is provided in the upper opening of the container 1 in a liquid-tight manner by caulking the container 1 or the like, and a positive electrode terminal 9 is fitted into the center of the insulating sealing plate 8. Have been. The positive terminal 9 is connected to the positive electrode 4 of the electrode group 3 via a positive electrode lead 10. In addition, the negative electrode 6 of the electrode group 3 is connected to the container 1 as a negative electrode terminal via a negative lead (not shown).

Comparative Example 1 Manganese trioxide (Mn ₂ O ₃ ) and lithium carbonate (Li)
₂ CO ₃ ) was blended to have a composition of LiMn ₂ O ₄ , mixed well in a mortar, and then heat-treated at 900 ° C. in air for 10 hours. X-ray diffraction measurement of the obtained product confirmed that a LiMn ₂ O ₄ phase was present. A non-aqueous solvent secondary battery similar to that of Reference Example 1 was assembled except that this product was used as a positive electrode active material.

The non-aqueous solvent secondary batteries of Reference Example 1 and Comparative Example 1 were repeatedly charged and discharged at a charging current of 300 mA to 4.3 V and discharged at a discharging current of 600 mA to 3.0 V. Further, the discharge capacity was measured while changing the discharge current value. The results are shown in FIGS. FIG. 2 is a diagram showing charging characteristics of the batteries of Reference Example 1 and Comparative Example 1, and FIG.
Is a diagram showing the relationship between the discharge current value and the discharge capacity of each battery, and FIG. 4 is a diagram showing the discharge capacity with respect to the number of charge / discharge cycles of each battery.

Example 1 Cobalt carbonate (CoCO ₃ ) and lithium carbonate (Li ₂ C)
O ₃ ) and lithium phosphate (Li ₃ PO ₄ ) with Li: C
o: P = 1.15: 1: 0.05, and mixed well in a mortar.
Heat treatment was performed for 0 hours. X-ray diffraction measurement of the obtained product confirmed that a LiCoO ₂ phase was present.
Reference Example 1 except that such a product was used as a positive electrode active material.
A non-aqueous solvent secondary battery similar to the above was assembled.

Comparative Example 2 Cobalt carbonate (CoCO ₃ ) and lithium carbonate (Li ₂ C)
O ₃ ) and Li: Co = 1: 1 in a molar ratio and thoroughly mixed in a mortar.
Heat treated for hours. X-ray diffraction measurement of the obtained product confirmed that a LiCoO ₂ phase was present. A non-aqueous solvent secondary battery similar to that of Reference Example 1 was assembled except that this product was used as a positive electrode active material.

The non-aqueous solvent secondary batteries of Example 1 and Comparative Example 2 were repeatedly charged and discharged at a charging current of 300 mA to 4.3 V and discharged at a discharging current of 600 mA to 3.0 V. Further, the discharge capacity was measured while changing the discharge current value. The results are shown in FIGS. FIG. 5 is a diagram showing the charging characteristics of the batteries of Example 1 and Comparative Example 2, and FIG.
Is a diagram showing the relationship between the discharge current value and the discharge capacity in each of the batteries, and FIG. 7 is a diagram showing the discharge capacity with respect to the number of charge / discharge cycles of each battery.

As is apparent from FIG. 5, the battery of Example 1 has a charging voltage of 50 to 100 m compared to the battery of Comparative Example 2.
It can be seen that V can be lowered, and deterioration of the electrolytic solution can be suppressed. In addition, as is clear from FIG. 6, the battery of Example 1 can improve the discharge capacity at a large current discharge as compared with the battery of Comparative Example 2. Furthermore, as is clear from FIG. 7, it can be seen that the battery of Example 1 can significantly improve the cycle life as compared with the battery of Comparative Example 2.

Example 2 Nickel carbonate (NiCO ₃ ) and lithium carbonate (Li ₂ C)
O ₃ ) and lithium phosphate (Li ₃ PO ₄ ) with Li: N
i: P = 1.15: 1: 0.05, and the mixture was sufficiently mixed in a mortar.
Heat treatment was performed for 0 hours. X-ray diffraction measurement of the obtained product confirmed that a LiNiO ₂ phase was present.
Reference Example 1 except that such a product was used as a positive electrode active material.
A non-aqueous solvent secondary battery similar to the above was assembled.

Comparative Example 3 Nickel carbonate (NiCO ₃ ) and lithium carbonate (Li ₂ C)
O ₃₎ and a Li: Ni = 1: formulated to be 1 molar ratio, were thoroughly mixed in a mortar, in air, 10 at 900 ° C.
Heat treated for hours. X-ray diffraction measurement of the obtained product confirmed that a LiNiO ₂ phase was present. A non-aqueous solvent secondary battery similar to that of Reference Example 1 was assembled except that this product was used as a positive electrode active material.

The non-aqueous solvent secondary batteries of Example 2 and Comparative Example 3 were repeatedly charged and discharged at a charging current of 300 mA up to 4.3 V and at a discharging current of 600 mA up to 3.0 V. Further, the discharge capacity was measured while changing the discharge current value. The results are shown in FIGS. FIG. 8 is a diagram showing charging characteristics of the batteries of Example 2 and Comparative Example 3,
FIG. 9 is a diagram showing the relationship between the discharge current value and the discharge capacity of each of the batteries, and FIG. 10 is a diagram showing the discharge capacity with respect to the number of charge / discharge cycles of each of the batteries.

As is apparent from FIG. 8, the battery of Example 2 has a charging voltage of 50 to 100 m compared to the battery of Comparative Example 3.
It can be seen that V can be lowered, and deterioration of the electrolytic solution can be suppressed. Further, as is clear from FIG. 9, the battery of Example 2 can improve the discharge capacity at a large current discharge as compared with the battery of Comparative Example 3. Further, as is clear from FIG. 10, the battery of the second embodiment can significantly improve the cycle life as compared with the battery of the third comparative example.

[0027]

As described above, according to the present invention, a non-aqueous solvent secondary battery having excellent charge / discharge cycle characteristics and high current charge / discharge characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing a cylindrical nonaqueous solvent secondary battery in Reference Example 1, Examples 1 and 2, and Comparative Examples 1 to 3.

FIG. 2 is a diagram showing charging characteristics of the batteries of Reference Example 1 and Comparative Example 1.

FIG. 3 is a diagram showing a relationship between a discharge current value and a discharge capacity in the batteries of Reference Example 1 and Comparative Example 1.

FIG. 4 is a diagram showing the discharge capacity with respect to the number of charge / discharge cycles in the batteries of Reference Example 1 and Comparative Example 1.

FIG. 5 is a diagram showing charging characteristics of the batteries of Example 1 and Comparative Example 2.

FIG. 6 is a diagram showing a relationship between a discharge current value and a discharge capacity in the batteries of Example 1 and Comparative Example 2.

FIG. 7 is a graph showing the discharge capacity with respect to the number of charge / discharge cycles in the batteries of Example 1 and Comparative Example 2.

FIG. 8 is a diagram showing charging characteristics of the batteries of Example 2 and Comparative Example 3.

FIG. 9 is a diagram showing a relationship between a discharge current value and a discharge capacity in the batteries of Example 2 and Comparative Example 3.

FIG. 10 is a graph showing the discharge capacity with respect to the number of charge / discharge cycles in the batteries of Example 2 and Comparative Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Stainless steel container, 3 ... Electrode group, 4 ... Positive electrode, 5 ... Separator, 6 ... Negative electrode, 8 ... Sealing plate, 9 ... Positive electrode terminal.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/02-4/04 H01M 4/50-4/58 H01M 10/40

Claims (4)

(57) [Claims] 1. A negative electrode comprising lithium, a lithium alloy or a compound containing lithium, LiCoO ₂ and Li
A non-aqueous solvent secondary battery including a positive electrode containing at least one selected from NiO ₂ as a positive electrode active material and an electrolytic solution obtained by dissolving an electrolyte in a non-aqueous solvent, wherein phosphorus is added as the positive electrode active material Non-aqueous solvent secondary battery characterized by using. 2. The non-aqueous solvent secondary battery according to claim 1, wherein the lithium-containing compound is a carbon material made of an organic sintered body doped with lithium ions. 3. The positive electrode active material comprising LiCoO ₂ to which phosphorus has been added comprises: (a) CoO, Co ₂ O ₃ , Co ₃ O
Cobalt oxide or cobalt carbonate selected from ₄ (C
oCO ₃ ), cobalt nitrate [Co (NO ₃ ) ₂ .4H ₂
O], (b) lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium nitrate (LiNO ₃ ) or lithium halide selected from lithium halide and (c) phosphorus (P) ) Or phosphorus pentoxide (P ₂ O ₅ ), lithium phosphate (Li ₃ PO ₄ ), lithium dihydrogen phosphate (LiH ₂ PO ₄ ), ammonium phosphate [(NH 4) ₃ PO ₄ .3H ₂ O] The non-aqueous solvent secondary battery according to claim 1, wherein the non-aqueous solvent secondary battery is obtained by heating and reacting a mixture with a selected phosphorus compound. 4. The positive electrode active material comprising LiNiO ₂ to which phosphorus has been added, comprises: (a) NiO, Ni ₂ O ₃ , Ni ₃ O
Nickel oxide or nickel carbonate selected from ₄ (N
iCO ₃ ), nickel nitrate [Ni (NO ₃ ) ₂ .6H ₂
O] and a lithium salt selected from (b) lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium nitrate (LiNO ₃ ) or lithium halide and (c) phosphorus (P) ) Or phosphorus pentoxide (P ₂ O ₅ ), lithium phosphate (Li ₃ PO ₄ ), lithium dihydrogen phosphate (LiH ₂ PO ₄ ), ammonium phosphate [(NH 4) ₃ PO ₄ .3H ₂ O] The non-aqueous solvent secondary battery according to claim 1, wherein the non-aqueous solvent secondary battery is obtained by heating and reacting a mixture with a selected phosphorus compound.